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2.5 THz GaAs Monolithic Membrane-Diode Mixer A New Planar Circuit Realization for High Frequency Semiconductor Components

Authors:
Peter H. Siegel, R. Peter Smith, Michael Gaidis, Suzanne Martin, Judy Podosek, Ute Zimmermann
Abstract:
A novel GaAs monolithic membrane-diode (MOMED) structure has been developed and implemented as a 2.5 THz Schottky diode mixer. The mesa-style planar diode uses a rectangular anode with a T-shaped metalization and a footprint that measures nominally 0.2µm by 1 µm. It is integrated onto a 3µm thick by 36µm wide by 600µm long GaAs membrane which bridges across an aperture in a monolithic all GaAs support frame approximately 50µm thick. RF filter structures are incorporated on the 600 µn long membrane. The membrane frame and RE circuit are coupled to an electroformed waveguide mount that places the diode across the center of a 2.5 THz full height rectangular waveguide (100x50µm²). The mixer mount contains an integrated Pickett-Potter feed horn and rectangular waveguide transformer, suspended-stripline single-mode RF filter channels to house the membrane, a fixed waveguide backshort for RF matching and a quartz-based transformer for the desired 7-21 GHz IF output Measurements of receiver performance, in air, yield a Treceiver of 20,000 K DSB at 8.4 GHz IF using a 150K commercial Miteq amplifier. The receiver conversion loss measures 17 dB (including air, diplexer, F filter and horn coupling losses), yielding a derived front-end noise temperature of approximately 12,500K DSB at 2514 GHz. A CO2-pumped methanol far-IR laser is used as a local oscillator at 2522 GHz and is injected with a Martin-Puplett diplexer. The required local oscillator power is below 3mW for optimum pumping, and no device damage was observed with incident power as high as 22mW. Improvements in noise temperature are expected as the devices and circuits are still being optimized The mixer is baselined for flight use on the Earth Observing System Microwave Limb Sounder instrument to measure 02 at 2502 GHz and OH at 2510 and 2514 GHz. E0S-MLS is scheduled for launch in 2002 on the Chem I platform, as part of NASA's Mission to Planet Earth.
Categories:
Mixers, Schottky Devices
Year:
1998
Session:
4
Full-text:
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Page Number(s):
147-159